Wellington, March 18 : Kane Williamson and Henry Nicholls slammed double centuries while sharing a mammoth partnership of 363 as New Zealand punished Sri Lanka's hapless bowlers to declare at 580/4 and dominate the play on day two of the second Test at the Basin Reserve, here on Saturday. At stumps, Sri Lanka were 26/2, with Matt Henry and Doug Bracewell taking a wicket each. The visitors now face an uphill task of avoiding a clean sweep in the two-match series after losing a thrilling first Test by two wickets on the last ball at the Hagley Oval in Christchurch last week. The standout players on Saturday's play were Williamson and Nicholls, who became the first teammates from the New Zealand Test team to score double-centuries in the same innings. During his remarkable 215, Williamson became the first-ever New Zealand player to reach the 8000 Test runs mark. Last month during the second Test against England in Wellington, Williamson had gone past former team-mate Ross Taylor's tally of 7683 runs to become the highest run-getter for New Zealand in Tests. The double ton by Williamson was also the sixth of his Test career, putting him at par with several greats like Marvan Atapattu, Virender Sehwag, Javed Miandad, Younis Khan, Ricky Ponting and Sachin Tendulkar. Among the players currently active, only Virat Kohli (7) has more double centuries than Williamson. After day one was marred by rain, New Zealand displayed tremendous attacking intent from the get-go on day two. Boundaries were flowing from the bat of Williamson and Nicholls as the duo put on a batting clinic, unbothered by both pace and spin of the Sri Lankan bowlers. The pair added 149 runs in the first session of the day with Williamson getting to 8000 runs and notching up his 28th Test ton in a space of four overs. Nicholls wasn't to be left behind as he got to his century in the session after lunch with the Kiwi onslaught in full flow. In just the second over after tea, Williamson brought up his double ton with a boundary -- much like he did to get to his 50 and 100 earlier in the day. Sri Lanka's agony finally ended thanks to Prabath Jayasuriya taking out Williamson and bringing an end to the marathon 363-run partnership. Nicholls continued to take the attack to Sri Lanka bowlers thereafter and brought up his maiden Test double century in just 240 balls. This was the 18th instance in Test cricket and the first time for New Zealand where two batters scored a double century in the same innings. New Zealand declared at 580/4 as soon as Nicholls got to his milestone and then made early inroads with the ball, leaving Sri Lanka reeling at 26/2 at stumps on day two, with captain Dimuth Karunaratne unbeaten at the crease. Brief Scores: New Zealand 580/4 dec (Kane Williamson 215, Henry Nicholls 200 not out) lead Sri Lanka 26/2 by 554 runs /IANS